DM8168平台中完成gv7601的spi总线驱动笔记

问1: 首先测试spi驱动自发自收，对应8168哪些管脚，如何配置spi功能？
答1：
    SPI_D0
    SPI_D1
    SPI_SCLK
    SPI_SCS0
    SPI_SCS1
    SPI_SCS2
    SPI_SCS3
    
    
arch\arm\mach-omap2\Board-ti8168evm.c

内核启动打印信息
[    0.340000] omap2_mcspi omap2_mcspi.1: registered master spi1
[    0.340000] spi spi1.0: setup: speed 48000000, sample leading edge, clk normal
[    0.340000] spi spi1.0: setup mode 0, 8 bits/w, 75000000 Hz max --> 0
[    0.340000] omap2_mcspi omap2_mcspi.1: registered child spi1.0

[    0.340000] omap2_mcspi omap2_mcspi.1: chipselect 0 already in use
[    0.340000] omap2_mcspi omap2_mcspi.1: can't create new device for spidev



改写后：
[    0.340000] omap2_mcspi omap2_mcspi.1: registered master spi1
[    0.340000] spi spi1.0: setup: speed 48000000, sample leading edge, clk normal
[    0.340000] spi spi1.0: setup mode 0, 8 bits/w, 75000000 Hz max --> 0
[    0.340000] omap2_mcspi omap2_mcspi.1: registered child spi1.0

[    0.340000] spi spi1.1: setup: speed 48000000, sample leading edge, clk normal
[    0.340000] spi spi1.1: setup mode 0, 8 bits/w, 75000000 Hz max --> 0
[    0.340000] omap2_mcspi omap2_mcspi.1: registered child spi1.1






//////////////////////////////////////////////////////////////////
注意：SPI_D[0]和SPI_D[1]好像要配置input和output，但是在这里没有配置
    一样可以自发自收
SPI Data IO. Can be configured as either MISO or MOSI
SPI_D[0]---PINCTRL171    0x4814 0AA8
SPI_D[1]---PINCTRL172    0x4814 0AAC


SPI 4803 0000h 4803 0FFFh 4KB Peripheral Registers
    4803 1000h 4803 1FFFh 4KB Support Registers

124h MCSPI_SYST McSPI system test register Section 16.3.10

9 SPIDATDIR1 Sets the direction of the SPI_D[1].
0 Output
1 Input

8 SPIDATDIR0 Sets the direction of the SPI_D[0].
0 Output
1 Input

SPI_D0-R76输入
SPI_D1-R77输出


问2：在做自发自收的时候，如果断开mosi和miso脚，用自带的spidev测试程序会打印发送的数据，
     如果把mosi和miso脚连接，就会接收全是0x00的数据，
     如果断开mosi和miso 打印的全是发送数据, 请问怎么回事？
     理论上应该是断开全是0x00，连接才是发送的数据 
     同时用示波器测量mosi和miso脚都有数据波形  
答2：其实这个问题是因为spi总线上负载gv7601引起的，如果去掉spi总线上的gv7601芯片
     短接mosi和miso，       miso就会收到mosi发送的数据
     如果断开mosi和miso，   miso就不会接收数据
     当时这个问题困扰我好几天，其实断开的话，miso接收到发送的数据也可以验证spi总线是正常的，
     因为gv7601的datasheet上说写数据的话
     During the write sequence, all Command and following Data Words input at the SDIN
     pin are output at the SDOUT pin unchanged
    
     
     
     

问3：omap2_mcspi_txrx_pio如何接收数据推送到应用层？
答3：  



////////////////////////////////////
16.3.11 McSPI Module Control Register (MCSPI_MODULCTRL)参考p1623

1 PIN34     Pin mode selection. This register is used to configure the SPI pin mode, in master or slave mode. If
            asserted, the controller only use SPI_D[0], SPI_D[1], and SPI_SCLK clock pin for SPI transfers.
            0 SPI_SCS[n] is used as a chip select.
            1 SPI_SCS[n] is not used. In this mode all related option to chip select have no meaning
            
            
注意把BTMODE2短接就可以从sd卡启动  


McSPI System Test Register (MCSPI_SYST) p1621
SPI Registers p1608  




问4:8bit和16bit在示波器波形图上不一样，为什么接收脚检测到数据是一样的？
    8bit时序图好理解，16bit如何理解？
spi mode: 0
bits per word: 16
max speed: 4000 Hz (4 KHz)
mydatabuffer[0]=0x6
mydatabuffer[1]=0x80
gv7601_read(1,0x06)=0x8006

mosi波形图bit7在前bit0在后
0x80  0x06


spi mode: 0
bits per word: 8
max speed: 4000 Hz (4 KHz)
mydatabuffer[0]=0x6
mydatabuffer[1]=0x80
gv7601_read(1,0x06)=0x8006

mosi波形图
0x06  0x80

答4：其实这就是数据按8bit和16bit发送的格式不同而已，
     本质上发送的内容还是一样的





//---------------------------------------------------------------
参考源代码：
///////////////////////////////////////////////////////
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

static uint8_t  mode;
static uint8_t  bits = 8;
static uint32_t speed = 2*1000;         //32*100*1000; //500000;
static uint16_t delay=0;





#if 0
//read operating
static int transfer_r(int fd,unsigned short addr)
{
	int ret;
    unsigned char  cmd[2];
    unsigned char  databuffer[4];
    unsigned char  mydatabuffer[2];
	struct spi_ioc_transfer	xfer[2];
	
	

    
    cmd[0] = addr & 0x00ff; 
    cmd[1] = 0x80 | (addr >> 8); 
    memset(xfer,0,2*sizeof(struct spi_ioc_transfer));
    memset(databuffer,0x00,2);
    xfer[0].tx_buf          = (unsigned long)cmd;
    xfer[0].rx_buf          = NULL;
    xfer[0].len             = 2;
    xfer[0].delay_usecs     = delay;
    xfer[0].bits_per_word   = bits;	
    xfer[0].speed_hz        = speed;
        
    
    
    xfer[1].rx_buf          = (unsigned long)databuffer;
    xfer[1].tx_buf          = NULL;
    xfer[1].len             = 4;
    xfer[1].delay_usecs     = delay;
    xfer[1].bits_per_word   = bits;	
    xfer[1].speed_hz        = speed;
    


    ret = ioctl(fd, SPI_IOC_MESSAGE(2), &xfer);
	if (ret == -1 )
	    printf("can't transfer");

	printf("databuffer[0]=0x%x\n",databuffer[0]);
	printf("databuffer[1]=0x%x\n",databuffer[1]);
	printf("databuffer[2]=0x%x\n",databuffer[2]);
	printf("databuffer[3]=0x%x\n",databuffer[3]);

	return ((databuffer[1] << 8) + databuffer[0]);
}
#else
static int transfer_r(int fd,unsigned short addr)
{
	int ret;
    unsigned char  cmd[2];
    unsigned char  databuffer[4];
    unsigned char  mydatabuffer[2];
	struct spi_ioc_transfer	xfer[2];
	
	

    
    cmd[0] = addr & 0x00ff; 
    cmd[1] = 0x80 | (addr >> 8); 
    memset(xfer,0,2*sizeof(struct spi_ioc_transfer));
    memset(databuffer,0x00,2);
    xfer[0].tx_buf          = (unsigned long)cmd;
    xfer[0].rx_buf      = (unsigned long)databuffer;
    xfer[0].len             = 2;
    xfer[0].delay_usecs     = delay;
    xfer[0].bits_per_word   = bits;	
    xfer[0].speed_hz        = speed;
        

	ret = ioctl(fd, SPI_IOC_MESSAGE(1), &xfer);
	if (ret == -1 )
	    printf("can't transfer");

	printf("databuffer[0]=0x%x\n",databuffer[0]);
	printf("databuffer[1]=0x%x\n",databuffer[1]);
	printf("databuffer[2]=0x%x\n",databuffer[2]);
	printf("databuffer[3]=0x%x\n",databuffer[3]);

	return ((databuffer[1] << 8) + databuffer[0]);
	
}
#endif












int gv7601_read(unsigned char chip_id,unsigned short addr)
{
	int fd;
	int ret ;
    char device[1024];
	
    memset(device,0x00,1024);
    sprintf(device,"/dev/spidev1.%d",chip_id);
    fd = open(device,O_RDWR);
    if (fd < 0)
        printf("can't open device");

	/*
	 * spi mode
	 */
	ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
	if (ret == -1)
		printf("can't set spi mode");

	ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
	if (ret == -1)
		printf("can't get spi mode");

	/*
	 * bits per word
	 */
	ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
	if (ret == -1)
		printf("can't set bits per word");

	ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
	if (ret == -1)
		printf("can't get bits per word");

	/*
	 * max speed hz
	 */
	ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
	if (ret == -1)
		printf("can't set max speed hz");

	ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
	if (ret == -1)
		printf("can't get max speed hz");

	printf("spi mode: %d\n", mode);
	printf("bits per word: %d\n", bits);
	printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000);	
		 		

    ret = transfer_r(fd,addr);
    close(fd);
	return ret;

}





int main(int argc, char *argv[])
{
    int tmp;

    while(1)
    {
        tmp = gv7601_read(3,0x06);
        printf("gv7601_read(1,0x06)=0x%x\n",tmp);
        sleep(1);
        
    
    }

    
    return 0;
    

}

问5：在spi应用中SPI_IOC_MESSAGE(1)和SPI_IOC_MESSAGE(2)，其中SPI_IOC_MESSAGE(2)为什么接收不到数据？
	//声明并初始化spi_ioc_transfer结构体
	struct spi_ioc_transfer tr = {
		.tx_buf = (unsigned long)tx,
		.rx_buf = (unsigned long)rx,
		.len = ARRAY_SIZE(tx),
		.delay_usecs = delay,
		.speed_hz = speed,
		.bits_per_word = bits,
	};

	//SPI_IOC_MESSAGE(1)的1表示spi_ioc_transfer的数量 
	ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);		//ioctl默认操作,传输数据
	///////////////////////////////
    xfer[0].tx_buf          = (unsigned long)cmd;
    xfer[0].rx_buf          = NULL;
    xfer[0].len             = 2;
    xfer[0].delay_usecs     = delay;
    xfer[0].bits_per_word   = bits;	
    xfer[0].speed_hz        = speed;
        
    
    
    xfer[1].rx_buf          = (unsigned long)databuffer;
    xfer[1].tx_buf          = NULL;
    xfer[1].len             = 2;
    xfer[1].delay_usecs     = delay;
    xfer[1].bits_per_word   = bits;	
    xfer[1].speed_hz        = speed;
    
    //xfer[0].rx_buf      = (unsigned long)mydatabuffer;

    ret = ioctl(fd, SPI_IOC_MESSAGE(2), &xfer);	
    为什么databuffer接收的数据全是0x00,用示波器测试接收脚有数据，如果通过ioctl(fd, SPI_IOC_MESSAGE(1)可以打印接收到数据
答5：其实相当于全双工和半双工通信方式，最好参考Timing获取答案    
    
    
	
    



////////////////////////////////////////////////////////////
问6：测试gv7601芯片的时候，如果是读寄存器，读的数据是0，如果是写寄存器，写什么就输出什么，
     现在的问题是为什么读寄存器读的数据是0呢？
     如果把standy引脚接地的话，有时候可以读出数据？
     
     比如datasheet中默认是非0数据，可是采用半双工方式读取的数据全是0呢?
006h FF_CRC_V   15      EDH Full Field CRC Validity bit.        R 0
     AP_CRC_V   14      EDH Active Picture CRC Validity bit.    R 0
     VD_STD     13-8    Detected Video Standard.                R 29
     RSVD       7-0     Reserved.                               R 255  
     
     mosi发送的16bit数据    0x80 0x06
     miso接收的数据应该是   0x80 0x06  寄存器值(非0)
     
     排查问题？p26
     1.字节顺序ok
     2.clk频率    不超过60MHZ ok
     3.Data Setup Time 和Data Hold Time  大于1.5ns ok
     
答6：这个问题困扰我一个多星期，后来发现是硬件引起的，因为你通过示波器检查读时序正常都没有问题
     应该把芯片的standby引脚接地，同时连接VCO_VDD上的一个电阻应该焊接100欧，可是错焊接成100K，
     电流太小，里面的模块工作有时不正常，所以表现为有时候可以读出数据，有时候不能读出数据

 
注意:     
4个gv7601并联在spi总线上，如果应用层读a-gv7601(CS为低电平)其中寄存器，但是b-gv7601(CS为高电平)的输出脚，会把输入数据照样输出
这样的话会冲掉读寄存器的值，所以datasheet建议采用串联方式菊花链 


/////////////////////////
如果频率为20000hz  两个spi数据包间隔也是100ms，现在make menuconfig中去掉spi的debug功能就没有占用很长时间了
因为打印下列debug信息占用很长时间  
[  182.960000] spidev spi1.3: setup: speed 11718, sample leading edge, clk normal
[  183.050000] spidev spi1.3: setup: speed 11718, sample leading edge, clk normal
[  183.140000] spidev spi1.3: setup: speed 11718, sample leading edge, clk normal
[  184.230000] spidev spi1.3: setup: speed 11718, sample leading edge, clk normal